Determination of the embryonic axes of Drosophila.
Determination of the embryonic axes of Drosophila.
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发表时间：
1991
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通讯作者：
C. Nüsslein-Volhard
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作者：
C. Nüsslein-Volhard
胚胎模式形成的原理已经在许多系统中使用经典实验方法进行了广泛研究。在果蝇中，遗传学和移植实验以及分子生物学的有力结合，有助于阐明在卵子发生和早期胚胎发生过程中起作用的机制，以建立早期胚胎中轴确定所需的一组位置线索。在对母体效应突变的系统性搜索中，已经鉴定出大约30个基因，它们特异性地影响胚胎轴确定的过程。这些“坐标”基因定义了四个系统，它们独立地确定前后（AP）轴（三个系统）和背腹（DV）轴（一个系统）。在前后轴上，前部系统确定头部和胸部的分节区域，后部系统确定腹部的分节区域，末端系统负责在卵的前端和后端形成不分节的末端，即头端和尾端。相比之下，背腹轴上的模式仅由一个系统确定。尽管所有四个系统使用不同的生化机制，但它们有几个共同的特性。（1）每个系统中一个基因的产物定位在刚产下的卵的特定区域，并作为一种空间信号发挥作用。（2）在每个系统中，这种空间信息最终导致一种作为转录因子发挥作用的基因产物的不对称分布。（3）这种转录因子以浓度梯度分布，该浓度梯度定义了一个或多个合子靶基因表达的空间界限。这三个前后系统以及背腹系统的共同作用确定了合子靶基因在前后轴上至少七个不同区域以及背腹轴上至少三个区域的表达。这些纵向和横向区域提供了一个粗略的空间预模式，然后通过合子模式基因的作用和相互作用进一步细化。
The principles of embryonic pattern formation have been studied extensively in many systems using classical experimental approaches. In Drosophila, a powerful combination of genetics and transplantation experiments, as well as molecular biology, have helped to elucidate the mechanisms that operate during oogenesis and early embryogenesis to establish a set of positional cues required for axis determination in the early embryo. In systematic searches for maternal effect mutations a small number of about 30 genes have been identified that specifically affect the process of determination of the embryonic axes. These 'coordinate' genes define four systems that determine the anteroposterior (AP) axis (three systems) and the dorsoventral (DV) axis (one system) independently. In the anteroposterior axis, the anterior system determines the segmented region of head and thorax, the posterior system determines the segmented abdominal region, and the terminal system is responsible for the formation of the nonsegmented termini at the anterior and posterior egg tips, the acron and telson. In contrast, pattern along the dorsoventral axis is determined by one system only. Although all four systems use different biochemical mechanisms, they share several properties. (1) The product of one gene in each system is localized in a specific region of the freshly laid egg and functions as a spatial signal. (2) In each system, this spatial information finally results in the asymmetrical distribution of one gene product that functions as a transcription factor. (3) This transcription factor is distributed in a concentration gradient that defines the spatial limits of expression of one or more zygotic target genes. The combined action of these three anteroposterior systems as well as the dorsoventral system defines the expression of zygotic target genes in at least seven distinct regions along the anteroposterior and at least three in the dorsoventral axis. These longitudinal and transverse domains provide a coarse spatial prepattern which is then further refined by the action and interaction of zygotic pattern genes.